1 Field of Invention
This invention relates to gas engines, specifically to an improved device to convert gas engines to operate on compressed natural gas. The present invention provides a novel system for increasing output power of compressed natural gas engines. The invention can be applied on dedicated, duel diesel, bi-fuel spark ignition, and four or two stroke gas engines.
2. Description of Prior Art
Currently the conversion of conventional engines to natural gas fueled engines is accomplished by modifying the existing engine. These methods are associated with loss of engine power, significant design modification, difficulty in optimizing operation, requirements necessitating adjustments of engine valve timing, complex additions to engine design, increases to engine weight and an overall rise in maintenance costs. Additionally, such systems do not provide for safety shutdowns when using natural gas. The prior art systems also provide a wide range of air to fuel ratios to meet the changing demand of speed and torque which cause exhaust emissions to exceed acceptable limits.
The present invention draws from a method used in steam generation, fluid injection, and combustion engineering fields. No prior art device has successfully addressed the application of such systems to an internal combustion engine. In several patents, the energy generated by the pressure of the gas inside the storage cylinders is used to improve engine performance. No patents use this energy to induce more air into the engine thereby allowing more fuel to burn and increasing engine power output as the present invention discloses.
Yul et al. U.S. Pat. No. 5,329,908 discloses a gas fuel injector with a gas accumulator. The electronically controlled system provides a variable fuel injection timing inside the engine cylinder. The injection timing varies from near the top dead center as in a diesel engine to near the bottom dead center, as in a gasoline engine. The system is designed mainly to maintain high efficiencies under variable supply pressures inside the storage tanks. The main deficiency of this invention is the added complexity to the engine design.
In U.S. Pat. No. 5,067,467 of Hill et al. a device is disclosed for compressing and injecting gaseous fuel from a variable pressure supply. The device utilizes energy from the gas in the engine chamber or from an external compressor to raise the pressure of the natural gas fuel needed for injection. The system is designed to compensate for decreasing supply pressures caused by the natural gas being consumed by the engine. This invention varies from the present invention because the subject invention uses the high pressure of the raw natural gas stored inside the cylinders to push more air to the engine. Thus the decrease in the storage supply pressure will not affect the performance of the engine as in Hill et al.
The U.S. Pat. No. 5,315,981 of Ning et. al. discloses a method for converting a diesel engine to a natural gas engine using a new cam profile to cause an early closure of the intake valve thereby reducing the engine's maximum pressures while using a conventional blower for air supply. This method is not efficient because it reduces the amount of air to gas mixture charged to the engine. Whereas, the subject invention increases the amount of air to gas mixture and thereby increases the power output of a gasoline engine or a naturally aspirated diesel engine when converted to use with compressed natural gas instead.
U.S. Pat. No. 5,203,305 discloses a system that uses an electronic translator to convert conventional fuel injector control signals to alternative gaseous fuel injectors. U.S. Pat. No. 5,228,423 relates specifically to duel-fuel gasoline engines. This invention discloses an improved intake passage and appropriate lift of the intake valves to minimize deviation in engine performance when switching from one fuel to another. U.S. Pat. No. 5,450,832 discloses a duel fuel system able to utilize the original electronic fuel injection design to regulate and deliver compressed natural gas. U.S. Pat. No. 5,325,894 discloses a method for fueling vehicles with liquefied natural gas after it has been warmed up in a heat exchanger. U.S. Pat. No. 5,408,957 relates to a gas injection system for conventional reciprocating or rotary internal combustion engines or turbines. All of these inventions are designed to minimize the loss in power when switching from conventional fuels to natural gas or to regulate the fueling systems. However, not one of them has any similarity to the subject invention in where engine power is increased by using the available compressed natural gas energy to "supercharge" the engine. In all the above-mentioned patents, there is no disclosure of a method of handling the essential problem of how to compensate for engine power loss when using compressed natural gas instead of liquid fuels. The present invention describes a method to increase engine power and improve engine performance by pressurizing the fluid flow (air) and by using the kinetic energy of another fluid (natural gas).